do you think an 80% in Quant is achievable in 45 days?
Yes! If not 80%, you can definitely come closer to it. Concentrate on the basics of all the areas that are tested in Quant and work on all the problems in OG. It should take you to 45+ is quant. Each person is different from the other in the strengths. So it depends on how deep you can go and how quickly to take it beyond 45.
Read through some of the suggestions to take the score to various levels in Quant. Those will be helpful.